Collapsible mandrel

ABSTRACT

A collapsible mandrel is provided for use, for example, in the production of filament wound containers and has retractable side walls which are operative in such a manner as to permit the walls to be peeled-away from contact with the interior of a finished container so that the mandrel can be quickly and easily removed from the interior of the container and readily reusable for the production of another container. Retraction of the side walls is accomplished by the provision of a primary and secondary lever or linkage assembly. The secondary linkage assembly is operatively connected to the side walls of the mandrel while the primary linkage is connected to and controls the movement of the secondary linkage by means of a fluid power actuated cylinder.

United States Patent Saidla Aug. 28, 1973 1 1 COLLAPSIBLE MANDREL PrimaExaminer-Bill S. Ta lor 5 l t w. D dl w y Y [7 I or m yomlssmgAttorney-Harold D. Shall et al.

Hill, Pa. [73] Assignee: Dana Corporation, Toledo, Ohio 221 Filed: July12, 1971 [57] ABSTRACT [21] Appl. No.: 161,804 collapsible mandrel isprovided for use, for example, In the production of filament woundcontainers and has retractable side walls which are operative insuch a[52] US. Cl 242/1, 156/425, 242/72, manner as to permit the walls to bepee|ed away f [5 l 1 I t Cl B2 81 contact with the interior of afinished container so that n the mandrel can b uick| and 635 removedfrom [58] Field of Search 242/1, 72, 110.1, the interior f the 2 and greusabk f 242/1 10; 249/180, 178, 185; 156/173, 1 5, the production ofanother container, Retraction of the 443, 446 side walls is accomplishedby the provision of a primary 56 R f C d and secondary lever or linkageassembly. The second- 1 l e erences e ary linkage assembly isoperatively connected to the UNITED STATES PATENTS side walls of themandrel while the primary linkage is 3,074,140 H1963 Balcomb et aim249/180 x connected to and controls the movement of the sec- 2,507,924/1950 Morse 249/180 ondary linkage by means of a fluid power actuatedeyl- 3,143,306 8/1964 Dijkmans.... 156/425 X inder. 3,492,186 1/1970Young 156/425 FOREIGN PATENTS OR APPLICATIONS 4 Clams 8 Draw 365,205/1962 Switzerland 249/180 52 1 1 A 66 28 f 20 62 l4 64 (I'T 8 b 78 6 1132- I *'--|26 79\ U i 4 1 |O4 U I00 I02 86d 5 74 |54-- I58 I 8O I 8-88c 1 98b I i 98a -1 1 I"' -22. 22 I I I 30 t i 1 I K 20 90b 90a I5 2OCOLLAPSIBLE MANDREL BACKGROUND OF THE INVENTION 1. Field of theInvention. This invention relates generally to mandrels and moreparticularly to an improved collapsible mandrel for use in the filamentwinding of large container-like structures.

2. Description of the Prior Art. Much activity has taken place in recentyears in the area of filament winding and although there are numerousadvantages in structures made by this process, a major problem thatstill exists and up until this time has not been satisfactorily overcomeis the provision of a suitable reusable mandrel which (1) possessessufficient flexibility to permit ready removal; (2) possesses sufficientstiffness (rigidity) to permit effective use as a forming mandrel and(3) has the ability to withstand the temperatures encountered duringcuring of the resin used in such processes.

The foregoing discussion of the problems indicates that an idealsituation is to have a mandrel which can be reusable, one that can beeasily removed after the various winding operations have been completedand one that is made of a material which is light weight and alsocapable of withstanding the temperatures that are encountered during thecuring stages of the filament wound structure.

Known mandrel devices have taken many forms, e.g., solid types such asshown in U.S. Pat. No. 2,614,058, inflatable types as seen in U.S. Pat.No. 3,366,522, collapsible type structures as shown in U.S. Pat. No.3,524,780.

A mandrel related to the present invention is shown and described onpages 24 and 25 of a booklet published in 1968 by the University ofMichigan Architectural Research Laboratory entitled Research of P-tential or Advanced Technology for Housing." The mandrel assemblydisclosed in this publication is for use with filament wound units andcomprises plate-like wall sections which are hinged at the corners andat the center of each of its four sides. A plurality of spacedjackscrews extend from a cylindrical central member and are attached tothe center hinges of each side along the length of the mandrel; removalof the mandrel from the completed structure requires retracting of theside sections by the jackscrews.

This latter design, while being much more satisfactory than thepreviously mentioned mandrels, still possesses certain drawbacks such ashaving many hinges and requiring the individual operation of a pluralityof jackscrews in order to collapse or retract the sides so that themandrel can be removed from the completed structure.

SUMMARY OF THE INVENTION The above mentioned problems and disadvantageshave been solved by the present invention by providing a collapsiblemandrel having side walls comprising quarter sections which are hingedat the center of the upper and lower walls and engageable at the centerof the side walls. Cooperating first and second linkage assemblies arecarried by one of the quarter sections and operatively connected to theremaining sections so that in the fully expanded or opened position theside walls form flush plate-like winding surfaces or sides. In thecollapsed position the hinged upper and lower wall sectons are pivotedwith respect to each other while the mating portions of the side wallsare movable inwardly with respect to each other. The expanding andcollapsing operation of the quarter sections is accomplished by means ofa centrally located hydraulically operated power cylinder which issecured at one end to one of the quarter sections and at the oppositeend to the first linkage assembly which in turn is connected to thesecond linkage assembly located at the opposite ends of the mandrel. Thepower cylinder is operative in its closed position through the linkageassemblies to maintain the quarter sections in a position where theirwinding surfaces are held flush in a position to have the filamentwinding applied. Actuating the power cylinder to its extended positioncauses the various linkage assembled to operate and draw the quartersections toward the center of the mandrel in a fashion which causes thesections to be peeled-away from contact with the interior of thecompleted unit.

It is accordingly an object of this invention to provide a mandrelhaving upper and lower walls which are pivotally connected and sidewalls which are movable relative to each other.

A further object of this invention is to provide a single means forcontrolling the collapsing of the walls of a mandrel.

A further object is to provide a collapsible mandrel having a system oflinks which operate to peel the walls completely free of the finishedproduct when being retracted to its collapsed condition.

Another object of this invention is the provision of a collapsiblemandrel which is made up of a plurality of substantially identicalsections. These and other objects, features and advantages of thepresent invention will become more fully apparent from the followingdescription of the preferred embodiments of the invention taken togetherwith the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view of the mandrel of the present invention inits expanded condition;

FIG. 2 is a longitudinal sectional view taken substantially along thelongitudinal center of the mandrel shown in FIG. 1 with certainpartsshown in full and others broken away for a clearer understanding ofthe present invention;

FIG. 3 is a view similar to FIG. 2 but with the mandrel in its collapsedposition;

FIG. 4 is an enlargedend elevational view looking from the right of themandrel shown in FIG. 2;

FIG. 5 is an end view similar to FIG. 4 but with the support structureremoved to more clearly see the linkage system;

FIG. 6 is a view similar to FIG. 5 showing the mandrel in its collapsedposition;

FIG. 7 is an enlarged partial view of the center pivot assemblyillustrated in FIGS. 4 through 6;

FIG. 8 is a side elevational view of the center pivot assembly shown inFIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, FIG.1 shows a mandrel 10 comprising a longitudinally extending body havingan upper portion, shown generally at 11 including quarter sections 12and 14 and, a lower portion 15 including lower quarter sections 16 and18. A central longitudinal extending hinge 28 pivotally connects theupper quarter sections 12 and 14 while a similar central longitudinallyextending hinge 30 pivotally interconnects the lower sections 16 and 18(as seen in FIGS. 4 and 6). Each quarter section is formed withlongitudinally extending flat side wall portions 20-22 which aredisposed at right angles and, when the quarter sections are assembled inabutting engagement, they make up the smooth plate-like winding surfacesof the mandrel. The adjacent side wall portions 20 and 22 may be formedin one piece or of two separate pieces which have been suitably joinedas by welding. A plurality of spaced longitudinally extendingreinforcing ribs 24 extend along the length of the interior or each wallportion 20 and 22 of the quarter sections l2, 14, 16 and 18 andterminate short of the outer ends thereof into abutting engagement withangled plates 26; additional plates 26 are arranged along the length ofthe mandrel at spaced intervals to provide added rigidity to thestructure. Both ribs 24 and plates 26 are secured to the side walls20-22 in a suitable manner, such as by welding.

The parts thus far described are preferably made from aluminum in orderto provide a light-weight portable structure (heat resistant) and also asufficiently rigid structure capable of withstanding both radial andcircumferential forces.

Referring in greater detail to the structure disclosed in FIG. 4., itcan be seen that the quarter sections 12 and 14, making up the upperportion 11, are interconnected at the center of the top adjacent sidewalls 20-20 by means of the longitudinally running hinge 28 and that thequarter sections 16 and 18 making up the lower portion 15 areinterconnected at the center of the adjacent side walls 20-20 by thelongitudinally running hinge 30 while the side wall portions 22 of eachquarter section are adapted to be in abutting relation, at such time asthe mandrel is expanded, as shown by the reference numeral 23 to form acontinuous fiat surface.

As best seen in FIG. 2, a compound linkage assembly, shown generally at32, is provided adjacent the opposite ends of the mandrel 10 tointerconnect the upper and lower portions 11 and in such a manner as topermit the upper and lower quarter sectons to be pivoted about thehinges 28 and 30 so that the top walls will be pulled or collapsedslightly inwardly at the hinge connection, as seen in FIG. 6, while theends of the adjacent side walls 22-22 will break-away from contact witheach other by moving relative to each other in both a horizontal and avertical direction. This break-away feature is an important part of thepresent invention and will be discussed in greater detail later in thespecification.

This collapsing movement of the quarter sections 12, l4, l6 and 18 bythe opposed compound linkage assembly 32 is made possible by amanipulation ofa main lever or linkage assembly shown generally at 34which is controlled by means of a vertically extending power cylinder 36pivotally supported at its upper end by a bracket 39 fixed to theinterior of the wall 20 of the quarter section 12. The power cylinder 36is moved downwardly to its extended position, shown in FIG. 3 in awell-known manner such as by a suitable pressure fluid. The lower end ofthe cylinder 36 is operatively connected to the actuating linkage 34 ina manner to be discussed later.

As best seen in FIG. 2 the compound lever assembly 32 and cooperatingactuating lever assembly 34 comprise a system of levers or links whichare constructed and arranged in such a manner as to permit the precisegeometry of the levers or links and the relation between them to operateto transmit movement from the power cylinder 36 to the actuating leverassembly 34 and therefrom to the compound lever assembly 32 which inturn controls the movement of the upper and lower portions 11 and 15.Two positions are made possible by this construction, in one positionthe portions 11 and 15 comprising the quarter sections l2, l4, l6 and18, are rigidly held in their expanded position illustrated in FIGS. 2and 5 wherein the mandrel 10 is in a position to have a forming processtake place thereon, for exam ple, a filament winding process, or in thesecond position wherein it can be retracted or collapsed to the positionseen in FIGS. 3 and 6 with the mandrel 10 assuming a condition making itreadily removable from the structure formed thereon.

, More particularly, the actuating lever assembly 34 is locatedlongitudinally intermediate the spaced actuating lever assemblies 32.The power cylinder 36 has a piston rod 38 which has its remote endpivotally connected to the bracket 39 and a piston 40 at its oppositeend operatively disposed within a cylindrical housing 42. The lower-mostportion of the cylindrical housing 42 has a clevis 44 for pivotallyreceiving the inner ends of a pair of outwardly extending links orlevers 46 and 48 which are a part of the actuating lever assembly 34 andare adapted to be connected to and thereby control and translatemovement to the compound lever assemblies 32 located at opposite ends ofthe mandrel 10. The various operating parts of the compound leverassemblies 32 are identical and accordingly the following descriptionand discussion will be made with reference to only one of theassemblies.

In order to translate the movement of the links 46 and 48 to thecompound lever assembly 32, a secondary guiding lever or link 50 ispivotally connected at its outer end at 51 to the levers 46 and 48 at apoint substantially intermediate the ends thereof. The opposite or innerend of the secondary link 50 is pivotally connected at 53 to the bracket39 which serves as one of a pair of relatively stationary fixed reactionpoints in the linkage or lever system.

A second relatively stationary or fixed point in the linkage or leversystem is provided by a bracket 52 (for each of the lever assemblies 32)which is axially aligned with but spaced longitudinally outwardly fromthe bracket 39. The brackets 39 and 52 are secured to the upper orinterior portion of the wall 20 of the quarter section 12 and as aresult this one quarter section can be considered a reaction member forthe entire lever system. Although both the actuating linkage assembly 34and the compound lever assembly 32 are supported at fixed points on thesame quarter section the operation of the various levers in the systemis such that, when the quarter sections are moved to their collapsedposition, this movement will draw the hinges 28 and 30 inwardly a slightdistance which will be sufficient to separate the mandrel from thestructure formed thereon.

The compound lever or linkage assembly 32 comprises a system of primaryand secondary levers which are pivotally connected at various points onthe quarter sections to permit the expanding and collapsing operationsto take place in response to movement of the actuating lever assembly 34by the power cylinder 36. More particularly, the lever assembly 32includes a first or main upwardly extending link 54 which is pivotallyconnected at its upper end at 56 to the outer end of lever 46 andpivotally connected at its opposite or lower end at 58 to a center pivotassembly 60 positioned at a point midway between the top and bottom ofthe expanded mandrel. A second link 62 is provided to connect the firstlink 54 to the stationary bracket 52. This is accomplished by having theinner end of link 62 pivoted at 64 to the first lever 54 at a pointsubstantially intermediate the ends thereof, while the outer end of link62 is pivotally connected at 66 to the bracket 52 thereby supporting themain lever 54 on the quarter section 12 and setting up the reactionpoint for the link age assembly 32 (primary lever system). These links54 and 62 and center pivot assembly 60 can be considered a primary leverportion of the assembly 32. Cooperating with these links 54 and 62 andcenter pivot assembly 60 is what is referred to as a secondary leverportion of the assembly 32.

As best seen in FIG. 5, this portion of the linkage assembly 32 isconnected to the center pivot assembly 60 which, when the mandrel isexpanded, is located substantially at the center of the quarter sectionsl2, 14, 16 and 18 and is operatively connected to the quarter sections12, 14, 16 and 18 through a plurality of links and levers making up thesecondary lever system of the actuating lever assembly 32.

The various links and levers in the secondary system are pivotallyconnected to the quarter sections 12, 14, 16 and 18 in such a manner asto be capable of drawing the sections inwardly to the position shown inFIG. 6, so that the side wall portions and 22 of each section will movegradually angularly inwardly with respect to the longitudinal axis x-xof the mandrel. This movement forms an important part of the presentinvention since it is most desirably in the filament winding ofstructures of this type to have the mandrel removed from the completedfilament wound structure in a manner which will not cause damage to theinterior surface thereof. Thus in the present invention, the side walls20 and 22, which form the winding surfaces, are capable of beingpeeled-away gradually from contact with the interior of the structuremaking it a very desirable arrangement.

The secondary lever portion of the actuating lever assembly 32 comprisesa pair of opposed radially outwardly extending control arms or levers 68and 70 having their inner ends pivotally secured at 72 to the centerpivot assembly 60 (clearly seen in FIGS. 7 and 8). The outermost ends ofthe control arms 68 and 70 are pivotally connected at 74 and 76,respectively, to the inner ends of a pair of opposed upwardly anddownwardly extending connecting links 78 and 80 for control arm 68 and82 and 84 for control arm 70. The outermost ends of arms 68 and 70 areprovided with arcuate cam surfaces 73 and 75 respectively, which areadapted, when the mandrel is in its fully expanded position, to bearagainst the adjacent faces of a pair of Iongitudinally extending guidemembers 79 and 81 secured to the quarter sections 16 and 18 at theirfree ends. The guide members further serve as a means to accomplish theflush engagement between the mating side walls 22-22 when the mandrel 10is in its expanded condition. The outer portions of each link 82,

78, 84 and 80, respectively, are pivotally connected at 86a, 86b, 86cand 86d to a plurality of suitable supports 88a, 88b, 88c and 88d fixedat spaced locations on one of the plates 26 associated with each of thequarter sections l2, l4, l6 and 18 at points above and below atransverse axis zz adjacent the inner faces of side walls 22. Alsospaced further below the transverse axis zz and inwardly toward thevertical axis y-y are similar rigid supports 90a and 90b secured to thesame plates 26 as the supports 88c and 88d respectively. Supports 90aand 90b are connected to arms and 68 through a short link 92 and 94 andan angularly extending link 102 and 100, respectively. The links 92 and94 are pivotally connected at 960 and 96b to the supports a and 90b atone end and the other end pivotally connected at 98a and 98b to theangularly extending arms 102 and which in turn have a pivotal connectionat 104a and [04b with the lower portion of arms 70 and 68 adjacent theouter ends thereof.

For a clearer understanding of the parts associated with the centerpivot assembly 60, reference can be made to FIG. 8 where it can be seenthat the inner end of the arm 68 is rotatably journalled on pivot pin 72by :means of a female portion 106 and the inner end of arm 70 isrotatably journalled on pivot pin 72 by a male portion 108.

Rigid supports are provided at opposite ends of the mandrel 10 forcooperating with the opposed center pivot assemblies 60 to function as aguide means therefor. As best seen in FIGS. 7 and 8 the center pivotassembly 60 has a-supporting bracket 136 including a pair of spaceddownwardly extending ears 138, 138 which are adapted to pivotallysupport the pivot pin 72 while the supporting bracket 136 carries pivot58 for pivotally connecting thereto the inner end of link 54. Asmentioned earlier the female and male portions 106 and 108 of horizontalarms 68 and 70 are also pivotally connected to the pivot pin 72intermediate the ears 138. A space is provided between the portions 106and 108 of the arms 68 and 70 and the ears 138,138 for rotatablymounting therein, on the pin 72, a pair of spaced rollers 140. Thefunction of the rollers 140 in the operation of the mandrel will bediscussed in greater detail later in the specification. For a clearerunderstanding of the support, structure and associated linkage referencewill be made throughout the following description to the longitudinallyextending central axis x-x as shown in the side elevational view of themandrel in FIG. 2 and a vertical axis yy and a transverse axis zz shownin the end view of the mandrel illustrated in FIGS. 4 and 5.

Referring first to the end view of the mandrel 10 of FIG. 4, it will beseen that each quarter section l2, 14, 16 and 18 includes asubstantially right angle connecting or support structure showngenerally at 110, 112, 114 and 116 and a diagonal brace 118, 120, 124and 122, respectively.

The right angle support structure associated with the quarter section 12includes a vertically extending angle member 126 and a transverselyextending angle member 128 located a distance to the right of the vertical axis yy equal to one-half the diameter of the rollers andterminating a substantial distance above the transverse axis zz. Themember 126, at its upper end, is secured, as by welding, to the interiorof the top wall portion 20 and adjacent its inner end is secured, as bywelding, to the transverse angle member 128; the

inner end extending beyond this connection to a position just above theaxis zz. The transverse member 128 has its right or outer end secured tothe interior of the side wall portion 22 adjacent one side of one of thelongitudinally extending ribs 24 while an extension 130 is secured onthe inner end thereof and projects beyond its connection with thevertical member 126; the extension 130 terminating at a point to theleft of the vertical axis yy. The purpose of this extension 130 will bediscussed hereinaften The right angle support 1 12 associated with thequarter section 14 includes a vertically extending angle member 132 anda transversely extending member 134. The vertical member 132 is similarin structure to the adjacent member 126 but reversed and spaced adistance to the right or in front of the vertical member 126 when viewedin FIG. 2. The vertical member 132 is located to the left of thevertical axis yy a distance equal to one-half the diameter of therollers 140 so as to have the opposed flat facing surfaces 142 and 144of the vertical members 126 and 132 aligned with and adapted to be inrolling engagement with the spaced rollers 140 of the center pivotassembly 60 as seen in FIG. 7, when the rollers move upwardly.The'vertical member 132, at its upper end, is secured, as by welding, tothe interior of the top wall portion 20 and adjacent its lower end issecured, as by welding, to the transverse member 134. The lower end ofthe member 132 extends beyond the member 134 and terminates just abovethe axis zz. The transverse member 134 is located above the axis z-z andis secured at its inner or right end to the vertical member 132 whilethe outer end thereof is secured to the interior of the side wall 22 ofquarter section 14. Thus, as seen in the end view in FIG. 5, the spacingof the vertical members 126 and 132 is such that the rollers 140 willride upwardly along the faces 142 and 144 as the linkage is being movedto a collapsed position causing the center pivot assembly 60 to beraised upwardly. The spacing allows one of the rollers 140 to ride upthe surface or face 142 of the vertical member 126 while the oppositespaced roller 140 rides up the surface or face 144 of the verticalmember 132. It will be evident that during such movement the quartersections 12 and 14 are restrained by the rollers from pivoting inwardlyabout their hinged connection 28 since the surfaces 142 and 144 areparallel. In order to permit the required relative pivotal movement totake place between the quarter sections 12 and 14 further means isprovided on the surfaces or faces 142 and 144 of the vertical members126 and 132 which will enable the rollers 140 to allow inward angularmovement to occur between the pivotally connected quarter sections 12and 14. This means takes the form of an outwardly sloping, inclined camsurface 146 on the vertical member 126 and an opposed outwardly slopinginclined surface 148 on the vertical member 132. As the rollers continueto move upwardly along the surfaces 142 and 144, they will come incontact with and ride along the cam surfaces 146 and 148 permitting thequarter sections 12 and 14 to pivot about the hinge 28 moving the lowerends of the sections 12 and 14 downwardly toward the axis zz and towardeach other. Downward movement begins at the hinge 28 which is only drawnin a short distance along the axis y-y while the upper sides 2020thereof move away from their original position a distance whichincreases as the distance from the hinge increases. This movement, whenoccurring with the completed container surrounding the mandrel, resultsin what can be considered as a gradual peeling away of the outersurfaces 20 of the quarter sections 12 and 14 as the sections pivotabout hinge 28 and the side wall portions 22 are drawn inwardly at theirfree ends 23 by the links 78 and 82.

Referring now to the extension provided on the transverse member 128, itis seen in FIG. 4, that the extension 130 terminates at the left of ortransversely outwardly of the vertical member 132. An angle or guidemember is secured to the outermost part of the transverse member 128 andengages the outer side of the vertically extending member 132 to limitoutward movement of the vertical members 126 and 132 be yond that shownin FIG. 4 when the container 10 is fully expanded.

The rigid supports for the quarter sections 16 and 18 comprise the rightangle structures 116 and 114 and associate braces 124 and 122respectively. The right angle structure 114 includes a verticallyextending angle member 154 and a mating transversely extending member156, while the right angle structure 116 includes a vertically extendingmember 158 and a mating transversely extending member with the matingmembers secured together, as by welding, adjacent the inner end or apexto form a right angle. The outer ends of the transverse members 156 and160 are secured, as by welding, to the interior of the side walls 22 andthe outer ends of the vertical members 154 and 158 are secured, as bywelding, to the'interior of the bottom walls 20 of the quarter sections18 and 16 respectively. The

vertical members 154 and 158 are in alignment with.

the vertical member 132 in the quarter section 14 and the verticalmember 126 in the quarter section 12 respectively. Thus, as seen in FIG.7, the spacing provides opposed faces 162 and 164 on the verticalmembers 154 and 158 which are engageable by the spaced rollers 140 ofthe center pivot assembly 60.

As shown in FIG. 4, the inner ends of the members 154 and 158 stop shortof engagement with the opposed members 132 and 126 and the rollers 140are positioned in contact with the faces 162 and 164 of the lowermembers 154 and 158 when the mandrel 10 is expanded. A stop means, inthe form of an angle 166 is secured to the face 162 of the verticalmember 154 and serves as a lower locating means for the rollers 140 ofthe pivot assembly 60 when the mandrel 10 is in its fully expandedposition.

Referring to FIGS. 2 and 4, the diagonal members 118, 120, 122 and 124act as additional braces for the right angle structures 110, 112, 114and 116 respectively. The members 1 l8 and 122 are secured adjacent theinner end of the vertical members 126 and 154, respectively, and extendto the inside of and toward the corner of the quarter sections 12 and 18and being secured at the interior thereof at this location. The members120 and 124 have their inner ends secured to the right angle portions112 and 116 adjacent the apex thereof and extends angularly to the frontand to the corners of the quarter sections 14 and I6 and secured theretoat this location.

Means are also provided for preventing excessive relative movementbetween the quarter sections 16 and 18. To this end, as seen in FIG. 4,a transversely extending bracket 168 is secured to the vertical member158 at a point a short distance below the stop means 166 and projects tothe left of the vertical member 154 and terminates in a right angle arm170 adapted to engage the outer side of the member 154 to act as a stopagainst outward relative movement of members 154 and 158 beyond thatshown in FIG. 4 when the mandrel 10 is expanded. Similarly, the verticalmember 154 is also provided with a transversely extending bracket 172spaced below the bracket 168 and bracket 172 extends to the right andterminates in a right angle arm 174 adapted to engage the outer side ofthe vertical member 158.

OPERATION Assuming the mandrel 10 is in its fully expanded position asseen in FIGS. 1, 2, 4 and 5 and it is desired to collapse the same tothe position shown in FIGS. 3 and 6, the power cylinder 36 is actuatedin a well-known manner to cause the cylindrical housing 42 to be moveddownwardly to its fully expanded position, as seen in FIG. 3. As aresult of this movement the pivot 44, which is fixed to the lower end ofthe cylindrical housing 42, drives the inner ends of the levers 46 and48 down toward the bottom of the mandrel resulting in a somewhatscissoring effect to take place between the arms 46 and 48 and associatesecondary links 50 connected at 51 thereto and at 53 to stationarybracket 39. The scissoring or inward movement of levers 46 and 48results in the center pivot assemblies 60 moving upward toward the fixedbrackets 52. As the center pivot assembly 60 moves up, the inner ends ofthe arms 68 and 70 move upwardly as seen in FIG. 6. In moving to thislatter position, the pivots 74 and 76 at the outer ends of the arms 68and 70 and the adjacent pivots l04b and 104a there-on move inwardly andthereby tend to straighten angular arms 100 and 102 in an upwarddirection and at the same time inwardly collapse the upper and lowerconnecting arms 78-82 and 80-84 by the pivotal connection 74 and 76. Asthe arms 100 and 102 are moved upwardly, the movement is such thatpivots 98b and 98c at the lower ends thereof, is sufficient to drawlinks 94 and 92 slightly inward and by so doing results in pivots 96band 96a at the opposite end of links 94 and 92, moving the center of thehinge 30 a slight distance inwardly toward the center of the mandrel 10.Since the rollers 140 prevent relative angular movement of the sections12 and 14 until the rollers reach the cam surfaces 146 and 148, thesections 16 and 18 will move angularly inwardly, as seen in FIG. 6,before the sections 12 and 14. Additionally, links 80 and 84 are shorterthan links 78 and 82 and move the lower sections 16 and'l8 fartherinwardly than sections 12 and 14.

Each hinge 28 and 30 moves radially inwardly a distance sufficient tobreak the seal from the completed filament would structure and allowremoval of the mandrel in longitudinal direction. Also, it can beclearly seen in FIG. 6 that the previously mated ends 23 of the sides 22have moved inwardly relative to each other and the walls 20 and 22 havemoved angularly inwardly a sufficient distance to enable the mandrel tobe easily present invention greatly the completed structure. the

Due to the fact that filament winding processes impose rather largeforces on the mandrel it is necessary that the mandrel be constructed insuch a manner as to be capable of withstanding both radial andcircumferential loads. The present invention greatly lends itself tosuch a structure not only by the reinforcing means provided but alsothrough the location and arrangement of the various links used in thesystem. Thus the present invention provides a structure having thenecessary resistance for withstanding the excessive winding forcespresent in such devices.

The present mandrel design has many applications, for example: it can beused for constructing reusable shipping containers, van bodies and thelike; and also has potential applications for use in construction ofroom-size modules for housing use such as a module for high risestructures, school buildings and hospitals. Another possibility is thecombining of two or more such mandrels to produce larger structures.

From the foregoing, it can be seen that the present invention providesan improved durable and reliable collapsible mandrel which hassufficient flexibility to permit easy removal, possesses sufficientstiffness and has the ability to withstand very high temperatures.

The present invention is not limited to use in constructing a structureof rectangular configuration but with alterations to the quartersections is capable of handling a variety of forms such as circularcylinders. I

Thus, it shouldbe understood that the particular mandrel is shown by wayof illustration only and not as a limitation of the invention. Theprincipals and features of this invention may be employed in varied andnumerous embodiments without departing from the scope of the invention.

Having thus described my invention, what is claimed ll. A hollowcollapsible mandrel comprising a pair of opposed concave longitudinallyextending major sections, each of said major sections havingtransversely spaced and longitudinally extending free edges, with thefree edges of one major section being movable independently of the freeedges of the other major sec tion and with the free edges of one majorsection being disposed cooperatively wih the free edges of the othermajor section at such times as the mandrel is expanded, each of saidmajor sections comprising a pair of longitudinally extendingminor'sections, longitudinally extending hinge means pivotallyconnecting said minor sections, and linkage means connected to saidminor sections for pivoting the minor sections of each major sectioninwardly toward each other and for moving said hinge means toward eachother and collapsing said mandrel and for pivoting said minor sectionsaway from each other and for moving said hinge means away from eachother for expanding said mandrel to its expanded condition, said linkagemeans pivoting the minor sections of one of said major sections towardeach other a greater amount when collapsing said mandrel then saidlinkage means pivots the minor sections of the other of said major 2. Amandrel according to claim 1 wherein said major sections are halfsections.

3. A mandrel according to claim 2 wherein said minor sections arequarter sections.

4. A mandrel according to claim 3 wherein said mandrel is rectangularwhen viewed in transverse crosssection, and said quarter sections eachhave a right angled configuration.

1. A hollow collapsible mandrel comprising a pair of opposed concavelongitudinally extending major sections, each of said major sectionshaving transversely spaced and longitudinally extending free edges, withthe free edges of one major section being movable independently of thefree edges of the other major section and with the free edges of onemajor section being disposed cooperatively wih the free edges of theother major section at such times as the mandrel is expanded, each ofsaid major sections comprising a pair of longitudinally extending minorsections, longitudinally extending hinge means pivotally connecting saidminor sections, and linkage means connected to said minor sections forpivoting the minor sections of each major section inwardly toward eachother and for moving said hinge means toward each other and collapsingsaid mandrel and for pivoting said minor sections away from each otherand for moving said hinge means away from each other for expanding saidmandrel to its expanded condition, said linkage means pivoting the minorsections of one of said major sections toward each other a greateramount when collapsing said mandrel then said linkage means pivots theminor sections of the other of said major
 2. A mandrel according toclaim 1 wherein said major sections are half sections.
 3. A mandrelaccording to claim 2 wherein said minor sections are quarter sections.4. A mandrel according to claim 3 wherein said mandrel is rectangularwhen viewed in transverse cross-section, and said quarter sections eachhave a right angled configuration.